1. Field of the Invention
The present invention relates to a facsimile apparatus which transmits data through facsimile communication, a control method for the facsimile apparatus, a program for performing the control method, and a storage medium for computer-readably storing the program.
2. Description of the Related Art
Conventionally, a technique for transmitting facsimile data by performing facsimile communication with a partner's terminal through an exchanging system has been known. In this technique, a terminal on a transmission side (hereinafter called a transmission-side terminal) first seizes a public line (telephone circuit) to be used for the facsimile communication. Then, the transmission-side terminal, which could seize the public line, detects a dial tone signal received from the exchanging system. Here, it should be noted that the dial tone signal is a signal which is transmitted from the exchanging system to the transmission-side terminal to notify that communication (calling) can be performed, when it is detected by the exchanging system that an on-hook state of the transmission-side terminal has been changed to an off-hook state.
Then, the transmission-side terminal, which detected the dial tone signal, dials a telephone number of a terminal on a reception side (hereinafter called a reception-side terminal) which is the destination to which the facsimile data is to be transmitted, and also transmits a CNG (calling) signal. Here, it should be noted that the CNG signal is a signal which is first output before an operation comes into a facsimile procedure, and also is a signal which is to be transmitted to a transmission channel to notify that a calling station is a non-voice terminal. Then, the reception-side terminal, which received the CNG signal, returns a CED (called) signal to the transmission-side terminal. Here, it should be noted that the CED signal is a signal which notifies that a called station is a non-voice terminal. Subsequently, the transmission-side terminal, which received the CED signal, starts facsimile communication with the reception-side terminal.
Here, a method of detecting the dial tone signal by referring to frequencies and signal patterns thereof is known (for example, Japanese Patent Application Laid-Open No. 2002-232519). In this method, the frequencies and signal patterns of the dial tone signals to be detected have been stored previously, whereby a user can detect the desired dial tone signal by referring to the corresponding frequency and pattern previously stored.
However, such a related art as described above includes a following problem.
Here, the problem, which occurs in the related art, will be described in detail with reference to FIG. 10. For example, in a case where a terminal A transmits facsimile data to a terminal B, there is a possibility that a call for phone call is received from a terminal C different from the terminal B to the terminal A by chance at timing same as that when a line is seized by the terminal A. Like this, if the line seizing operation by the terminal A (1001) conflicts with the call reception from the terminal C (1002), a call from the terminal A to the terminal B is not performed. Instead, the line is connected between the terminal A and the terminal C (1003).
Then, it is conceivable that, after the line was seized, a voice signal for phone call is transmitted from the terminal C to the terminal A which is in a state (1006) of waiting for a dial tone signal from an exchanging system to transmit a dial signal (1004, 1005). Consequently, in the above related art, there is a fear that the voice signal transmitted from the terminal C is erroneously recognized by the terminal A as the dial tone signal transmitted from the exchanging system (1007). That is, in Japanese Patent Application Laid-Open No. 2002-232519, frequencies of the dial tone signal have previously been stored as a detection condition, and a signal which conforms to one of the stored frequencies is detected as the dial tone signal. Here, in FIG. 10, if the voice signal (1004, 1005) transmitted from the terminal C includes a signal of which the frequency conforms to the frequency included in the detection condition, the relevant voice signal (1005) is detected by the terminal A as the dial tone signal transmitted from the exchanging system.
Then, the terminal A, which erroneously recognized that the dial tone signal was received from the exchanging system, dials a telephone number of the terminal B which is a real (or right) destination (1008). Also, the terminal A transmits a CNG signal to the terminal B (1010). However, since the line has been already connected between the terminal A and the terminal C, the exchanging system does not recognize the dial signal to be transmitted to the terminal B, and the dial signal is thus transmitted to the terminal C (1009). In addition, the CNG signal from the terminal A is transferred to the terminal C as it is (1011).
Even in a case where the terminal C receives the CNG signal while performing phone call, it is assumed that the terminal C has a function to automatically change a phone call mode to a facsimile mode and transmit the CED signal for facsimile data reception. That is, the terminal C, which received the CNG signal from the terminal A (1012), automatically changes its phone call mode to the facsimile mode (1013), and transmits the CED signal to the terminal A (1014).
The terminal A which received the CED signal from the terminal C (1015) determines that the line connection with the terminal B has ended, starts facsimile communication, and thus transmits the facsimile data, which is to be originally transmitted to the terminal B, to the terminal C (1016). By such an operation, the problem that the facsimile data that a user of the terminal A originally intended to transmit to the terminal B is erroneously transmitted to the terminal C occurs. In particular, if the transmitted facsimile data includes a high-confidential important content, for example, a serious problem of leakage of confidential information occurs.